Further utilizing the AEC3 config struct for constants

BUG=webrtc:5298

Review-Url: https://codereview.webrtc.org/3007833002
Cr-Commit-Position: refs/heads/master@{#19605}
diff --git a/webrtc/modules/audio_processing/include/audio_processing.h b/webrtc/modules/audio_processing/include/audio_processing.h
index e130b83..03bd8c8 100644
--- a/webrtc/modules/audio_processing/include/audio_processing.h
+++ b/webrtc/modules/audio_processing/include/audio_processing.h
@@ -292,8 +292,14 @@
         struct EchoAudibility {
           float low_render_limit = 192.f;
           float normal_render_limit = 64.f;
+          float active_render_limit = 100.f;
         } echo_audibility;
 
+        struct RenderLevels {
+          float active_render_limit = 100.f;
+          float poor_excitation_render_limit = 150.f;
+        } render_levels;
+
         struct GainUpdates {
           struct GainChanges {
             float max_inc;